Alternating-current motor.



UNIT D STATES PAT T OFFICE.

ERNEST SCHWEIGER, or SGHENEGTADY, NEW YOR ASSIGNOR TO GEN-- EaAL-E Eormo COMPANY, A- ooRroEATIoN or NEW YORK.

LTER A ING-QU R NT moron. I

1 ail Z whom, it Indy concern:

. Be it known that I, ERNEST ,S'CHWEIGER, a subject of the King of Austria-Hungary, residing .at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Alterj Hating-Current Motors, of which the following is a specification.

My invention relates to alternating-current motors; and its object is to provide a novel structure for alternating-current motors which shall comprise means for properly commember it is possible to impress upon the motor a s'eeo nd-electromotive force by means of brushes displaced ninety electrical degrees from the 'short-circuiting brushes and that electromotive force will produce a torque in the motor which can be controlled in pensating voltage.

amount and direction. Furthermore, it is known that if the magnitude and phase of this voltage impressed upon the commutator be of proper values the magnetizing-current of'the motor may be compensated for and In order that the compensation should be the the power factor thereby improved.

proper amount for varying'speeds and loads of t e motor, it is necessary to vary the com- My invention consists in providing a novel motor structure for automatically obtaining the results described above without employing a second set of commutator-brushes.

My invention'will best be understood by reference to the accompanying drawings, in

. Fig. 5 as still "modification.

A which- Figure 1 shows a side elevation of'an alternating-current motor arrangedin accordance with my invention, a portion of the field structure being'broken away. Fig. 2 is a development of the rotor-winding, the commutator and brushes being indicated diagram-' .matically. ig. 3 is a'diagram showing a circuit arrangement: adapted to my invention. Fig.4 Hal-modification thereof, and

Specification of Letters Patent. Application filed May 2. 1904. Serial No. 205.849.

' Patented now-27, 1906.

In the drawings, S represents the stator or primary member of the motor, which is supplied with single-phase alternating current.

- R represents the rotor, which is provided .with a commutator C and the short-circuiting' brushes 7) b. Mounted on the same shaft with the rotor R is an auxiliary rotor T, which is in inductive relation to the auxiliary statorwinding 8 of the small rotor r and is connected to the winding of the main rotor R, as shown in Fig. 2. In this figure the rotorwindin R is developed on a plane surface and is shown as the well-known series type of winding. The winding r is shown as consisting of a similar winding, each coil being connected to an opposite coil on the main rotorwinding R. 0 represents the commutator, and b b the short circuiting brushes, of the main rotor. It will be seen that the developed winding, as shown, is adapted for a fourpole machine. v

It is evident from an inspection of Fig. 2 that any COll of auxiliarywindmg 1', the .ter-

minals of which are connected to points on the main winding R, which at any instant are opposite short-circuiting brushes b b, will have its circuit completed by theshort-circuiting brushes and their connections. the other hand, any coil of winding 1, the .termina'ls of which-are connected to points on the main winding R, which at any instant are midway between pairs of short-circuiting brushes b b, can have its circuit completed only through the main rotor-winding.

Referring now to Fig. 3, the connections of the various wiiidings are diagrammatically shown. S represents the main stator, which is connected in series with the auxiliary stator s to the source of current a a. R represents the main rotor, short-circuited by the brushes b b on the line of magnetization of the stator. r represents the auxiliary rotor, each conductor of which is connected to a directly-opposite conductor on the rotor R, as

has already been explained. It will be seen producesa magnetization on'the line of its brushes.

terminals. This produces an electrornotive force along the same line in the auxiliary rotor r, and since the conductors .of the rotor r are connected to the opposite conductors on the rotor-R this electromotive force, which is induced in rotor r on the line ofthe terminals of stator s, impresses an electromotiveforee on the main rotor R, displaced ninety electrical degrees from the line of short-circuited In other words, by means of the auxiliary stator and rotor an electromotive force is impressed upon the rotor R in the same manner as if an auxiliary. set of brushes were employed. Furthermore, it will be seen that this electromotive force 1s of the roper pha'se and magnitude for varying eeds and loads of the main motor. Since t e stator s is connected in series with the main stator S, the. field of stators is in phase with the currents in stator S and is also propjortional in magnitude to these currents. onsequently the electroniotive force induced in rotor r and impressed upon the main rotor R varies both in phase and magnitude with the motor-currents. It has been seen that this is one of the requisites for proper compensation. Furthermore, with a given strength of field in stator s the electromotive force induced in rotor 1 and impressed upon the rotor R- is inversely proportional to the speed of the main motor. As has been seen, this is the second requisite for proper compensation. 7, It has been said that for proper compensa tion the compensating electromotive force should vary in phase and magnitude with the motor-currents. S eaking more accuratelv, it should be said t at the variation should occur with the rotor-currents. In the arrangement of Fig. 3 the variation occurs with the stator-currents, which is only approximately correct, since the stator and rotor currents 0 not undergo precisely similar variations in magnitude and phase.

In the arrangement shown in Fig. 4 the auxiliarystator s is connected in series with the rotor R, and thereby variation of the auxiliary stator-field with the rotor-currents is secured. I

In addition to the electromotive force induced b transformer action in rotor r on the line of t e terminals of stator 8 there is a second electroinotive force induced in rotor r on a line at right angles to the line of the statorterminals 8, due to cutting the field of stator s. The current, due to this elcctromotivc force, passes directly through the short-circuiting brushes 1) b of the main rotor and has no effect upon-the magnetization of the main motor. It acts, however. to produce in the auxiliary motor or exciter a revolving field which becomes more uniform as the motorspeed approaches synchronism. This revolving eld serves to decrease the self-in duction of the rotor r, and thereby improves the power factor of the motor. 'With a single-phase excitation the revolving field is not absolutely uniform until synchronous speed is reached; but, if desired, the auxiliary motor or exciter'may be arranged to producea revolving field at all speeds. 'Thus. in Fig. 5 a further modificationis shown, in which the auxiliary rotor v" is excited by a polyphase stator 8 instead of the singlerphase stator heretofore shown. The polyphase stator s is connected to the single-phase source of supply and also toa phase-shifting device, such as a condenser K, in order to obtain a revolving field in the well-understood manner. With this arrangement the variation in voltage with variation in motor-speed is automatic, as'in the former arrangements; but the variation with the motor-currents must be obtained by varying the voltage impressed upon the stator s or by shifting the terminal connections. or both. These and other methods of regulations are well known in the art and re uires no further description.

In the iagrams I have shown the rotor R short-circuited directly upon the line of the stator magnetization, the tor ue-producing current being obtained wholly om the auxiliary rotor. With this arrangement, however, synchronism is the limiting speed for the motor, since at synchronism no electromotive force is induced in rotor r and no torque-producing current flows in rotor R. It' is by no means necessary, however, that the main rotor should be short-circuited directly upon the line of primary magnetization, but instead the brushes mav be shifted to a line at an angle to the line of primary magnetization, as in the-ordinary repulsionmotor. With this arrangement proper compensation may be obtained, as heretofore explained, while the operation of the motor at s eeds above synchronism may be secured, i desired. 4

"arious modifications may be made in the construction and arrangement of parts without departing from my invention, and in the appended claims I aim to cover all such modifications which are Within the spirit and scope of my invention.

What I claim as new, and desire to secure by Letters Patent of the United States, is

1. In anhlternating-current motor, a primary winding supplied with alternating current, a secondary Winding provided with a commutator and short-clrcuiting brushes, an auxiliary winding revolving with said secondary" winding and electrically connected thereto, and means for inducing in said auxiliary winding an electromotive force adapted to produce a compensating current in said secondary winding.

2. In an alternating-current motor, a primary winding supplied with alternating current, a secondary winding provided with a commutator and short-circuiting brushes, an

auxiliary winding revolving with said sec- 'ondary winding and electrically connected thereto, and means for inducing in said auxiliary winding an electromotive force adapted to produce a compensating current in said 5 secondary windings and having its maximum i value at points displaced approximately ninety electrical degrees from the short-ciri cuiting brushes: l

3. In an alternating-current motor, a prit inary winding supplied with alternating cur- 1 rent, a secondary Winding provided with a commutator and short-circuiting brushes, an auxiliarywinding revolving with said secondary winding and electrically connected i thereto, and means for inducing in the said auxiliary winding an electromotive force va- .rying inversely \n'th the speed of the motor.

4. In an alternating-current motor, a primary winding supplied withalternating current, a secondary winding provided with a commutator and short-circuiting brushes, an 1 auxiliary. winding'revolving with said seci ondary winding and electrically connected thereto, and means for inducing in said auxiliary winding-an electromotive force varying in magnitude and phase with the inotor-currents.

In an alternating-ailment motor, a primary winding supplied with alternating cur- 1 rent, a secondary winding provided with a commutator and short-circuiting brushes, an

j winding.

auxiliary winding revolving with said econdary winding and electrically conin-cted thereto, and means for inducing in said aux- 3 iliary winding an electromotivc force varying inversely with the motor speed and varying in phase and magnitude with the nmtor-currents.

6. In an alternating current motor, a 4 main stator-winding. a main rotor-winding provided with a commutator and short-circuiting brushes, an auxiliary stator-winding in series with one of said main windings. and

an auxiliary rotor-winding in inductive relations to sa1d auxihary stator-winding and electrically connected to sa1d mam rotor- 7. In a'n alternating-current motor. a main stator-Winding, a main rotor-winding 5 provided with a commutator and short-circuiting brushes, an auxiliary rotor-winding electrically connected to said main rotorwinding, and 'means for inducing in said auxiliary rotor-winding an electromotive force adapted to produce a compensating current in said main rotor-windingand diminishing as the speed of the motor increases.

In witness whereof I have hereunto set my hand this 30th day of April. 1904.

ERNEST SCl-IYEIGER. Witnesses:

BENJAMIN B. HrLL HELEX ORFoRn. 

